Machine for making open wire transmission line



Aug. 5, 1958 MACHINE FOR MAKING OPEN WIRE TRANSMISSION LINE Filed April3, 1952 EIIEE l J. D. GIULIE ET AL' 2,846,347

2 Sheets-Sheet l EIE- INVENTORS Joe 0 G/u/ie Les/le E Worcesfer ECKHOFFSLICK 1958 J. D. GIULIE ET AL 2,846,347

MACHINE FOR MAKING OPEN WIRE TRANSMISSION LINE States MACHINE FOR MAKINGUPEN WIRE TRANSMISSION LINE This invention relates to an open wiretransmission line, the machine on which such line can be manufactured,and to the process of manufacturing such line.

In carrying high frequency electric currents it has been long recognizedthat an ideal transmission line would consist of two parallel wires withonly air serving to separate and insulate the wires from each other.When transmission lines having two parallel wires have a solidinsulating material separating them, dielectric losses are encountereddue to the material used as an insulation. In addition, whensuch'transmission lines are exposed to the atmosphere, dirt and moisturefrom the air settle on the insulation, reducing the effectiveness of thetransmission line.

Of course, it is impossible to achieve a completely ideal line sincesome method must be used to space the wires and to support the line. Oneof the most effective and practical lines consists of two parallel Wireswith a series of insulating spacers holding the two wires in spacedrelationship. Such transmission lines are wellknown and the spacers maybe made from a plastic material having good insulating properties oreven from wood. However, the manufacture of such lines in the past hasbeen slow and tedious since the spacers have ordinarily been slotted andfastened on the line by hand. An attempt has been made in the past toproduce such lines using thermoplastic plastic spacers by heating theWire to above the softening point of the plastic and pressing the wireinto the unheated spacer. However, when such a method is used, thetemperature of the wire must be so high that it destroys the possibilityof using any corrosion resist-ant coating on the wire and an oxide filmis left on the wire. Even when using parallel wires with widelyseparated spacers, it is highly desirable to have a corrosion resistantvarnish or lacquer on the wire since, under severe operating conditions,corrosion products may be washed from the wire and onto the spacers,greatly lowering the effectiveness of the line. Further, such lines inthe past have had sharp edges on the ends of the spacers so that if oneattempts to roll up a section of such line, the spacers may becomeentangled with adjacent turns of the wire, making is diflicult to unrollthe wire.

It is therefore an object of the present invention to produce an openwire transmission line having widely separated spacers wherein the endsof the spacers are smoothly rounded, are firmly bonded to the wire, andwherein the wire itself may have acontinuous film of a corrosionresistant coating on its surface.

It is another object of this invention to provide a fully automaticmachine for making such transmission lines, said machine being ofrelatively simple construction, operating at a high rate of speed andrequiring substantially no labor other than the initial set-up of themachine.

Still another object of this invention is to provide a process formaking open wire transmission line wherein the wire is firmly bonded tothe spacers and a protective coating on the wire is not damaged duringthe manufacturing process.

In general, we accomplish the objects of this invention by providing anautomatic machine wherein the spacers are cut to the correct length froma length of plastic material, slot-ted, the wires inserted in the slots,the ends of the spacers heated, and the end-s sealed and rounded.

Referring now to the drawings forming -a part of this application, thereis shown in 4 Figure '1 a plan view of our improved machine fo makingopen wire transmission line.

In Figure 2 there is shown a detailed view on the lines 22 of Figure Iparticularly showing the cams which control the action of the cut-offsaw and feed mechanism of our improved device.

Figure 3 is a cross-section on the lines 3-3 of Figure 1.

Figure 4 is a cross-section on the lines 4--4 of Figure 3.

Figure 5 is a view, partially in cross-section, on the lines 55 ofFigure 1, showing the mechanisms for heating the ends of the plasticspacers and for crimping the ends of the spacers.

Figure 6 is a cross-section on the lines 6-6 of Figure 5, showing indetail the crimping mechanism.

Figure 7 is a cross-section on the lines 77 of Figure 6, showing anotherview of the crimping mechanism.

Figure 8 is .an enlarged perspective view of the coacting dies whichshape the/ends of the plastic spacers and crimp the spacers to the wire.

Figure 9 is a cross-section view on the lines 99 of Figure 5, showing aplasticspacer passing through the heating area of our device.

Figure 10 is a perspective view of the completed open wire transmissionlinemade in accordance with our invention.

Referring now to the drawings by reference characters, the machineproper consists of an elongated tablelike structure which is composed oftwo side members 12 and 14 suitably spaced apart and held firmly by aU-shaped center section 16. The table portions 12 and 14 are supportedby a suitable framework which has not been illustrated for purposes ofclarity. The members 12 and 14 may each be made from a single piece ofsuitable metal, such as steel, which extends the length of the machine,or they can be made in several sections and fastened together. On theinner edges of members 12 and 14 are slots 18 and 20 which serve toguide the workholders 22. The workholders 22 have a fiat base member 24which extends into the slots 18 and 20, ensuring that the workholderswill be supported in the proper relationship to the rest of the machine.The workholders 22 have a pair of upwardly extending arms 26 and 28attached to the basemember 24. The arms 26 and 28 each have a slot 32,which provides a recess of the proper size to hold a plastic spacer. Theslot 32 is defined by arms 34 and 36 and arm 34 is higher than arm 36for reasons which will be subsequently apparent. The base 24 of theworkholder 22 is attached to a suitable drive device such as an endlessroller chain 38, in order that the workholder may be propelled'along'the table members 12 and 14. The chain 38 is driven by a primemover, not shown. I

The endless chain 38 not only serves to convey the work-holders 22-alongthe bed of the machine, but also serves to operate two cams 40 and 42 intimed relationship with the work-holders, said cams serving to controlthe feed and cut-off of the plastic rod from which the spacers for theline are made. As can be seen from Figure 1, the cams 40 and 42 are on acommon shaft 44 which is driven by the chain 38 by means of gear 46 onshaft 44.

Turning now to the feed mechanism for the plastic red, the cam 40 isprovided with a cam follower 48 which is held in contact with the cam bymeans of spring 50. A slider 52 is mounted on track 53 and given areciprocating motion by the action of the cam follower 48 on the cam 40.The slider 52 is provided with a detent 54 which is held in contact withthe plastic rod 56 by means of spring 58. The end of detent 54 issharpened as shown, and is set at an angle, so that as the slider 52moves forward, i. e., toward the bed of the machine, the rod 56 isengaged by the detent 54 and advanced towards the machine. On the otherhand, as the slider 52 moves away from the machine, the detent 54exercises little friction on the plastic rod 56 and slides freely overit. A second detent 60 of similar construction and biased by spring 62is fastened to the body of the machine proper and offers substantiallyno resistance to the plastic rod 56 as it advances, but engages the rod56 and prevents it from moving away from the machine. Thus, as theslider 52 moves forward the plastic rod is engaged by detent 54 andbrought forward and as the slider 52 moves away from the machine, theplastic rod 56 is engaged by the detent 60 and is prevented from moving.

As will be seen in Figure l, the cam 40 has a relatively steep slope inthe portion which serves to advance the rod so that the rod movesforward quite rapidly and the slider moves'to the rear relativelyslowly.

The cam 42 is provided with a cam follower 64 which serves to controlthe position of the motor 66 and the circular saw 68, which is directlyconnected thereto. The motor 66 is pivotally mounted on the bed of themachine by shaft 67. It will be noted that the cam 64 raises the saw 68very rapidly and lowers it slowly so that the saw cuts slowly throughthe plastic rod and is then raised rapidly to an inoperative position.

In the position of the parts shown in Figures 1, 2 and 3, the saw hasjust completed its cut and is starting to rise. The synchronization ofthe parts is such that the rod 56 is advanced, while the saw is in araised position, the slider 52 is withdrawn as the saw starts its cut,and just as the saw completes its cut, the arm 34 of Workholder 22 ispresented to the cut-off plastic rod to carry it to the subsequentoperations. Mounted adjacent to the saw is a ramp-like structure 70having a shoulder 72 thereon. The shoulder 72 serves to hold the rod inposition as it is being sawed and a spring 74 further serves to hold therod against the shoulder 72. As the workholder 22 moves forward thehigher or trailing arm 34 of the workholder 22 engages the rod and pullsit along the ramp 70. Since the spring 74 is pressing downward on therod, as the workholder advances the severed rod 78 is brought down intothe recess 32 of the workholder into proper position for the subsequentoperations.

Mounted adjacent to the cut-oif device and ramp described, are two sawblades 74 and 76 mounted at an acute angle to the path of travel of theworkholder, as is shown in Figure 1. As the workholder advances, theplastic spacer 78-is brought in contact with the two saw blades so thata slot of suitable depth is cut in both ends of the spacer.

A source of wire is provided, not illustrated, and two wires 80 and 82are passed over rollers 84 and 86 and onto the body of the machine. Twoangular blocks 88 and 90 are provided to guide the wire into the bed ofthe machine, and covers 92 and 94 serve to hold the wire down into theproper position. The wire is further held in position by holders 96 and98 which are pivotally mounted slotted members. It will be noted thatthe wires are introduced into the path of the grooved spacers 78 in aline which would be a continuation of the saw blades 74 and 76. As thespacer 78 passes over the end of the saw blades 74 and 76, the wiresfall into the slots of the spacer and the holders 96 and 98 are pushedto each side. After the spacer 78 has passed the holders 96 and 98, theyspring back into the position illustrated.

, After the wires have been inserted in the slots of the spacers, it isnecessary to heatthe spacers in order that .4 they may be pressed downover the wire. It has been found that if the wire is cold it will notform a solid bond with the plastic spacers and the construction which weemploy serves to heat both the wire and the spacers so that the spaceris rendered soft enough to be readily deformed at its ends and the wireis hot enough to form a solid bond with the plastic. However, the wireis not heated to the extent that it would'destroy the thin, varnishlikeinsulation on the wire.

The wire and the spacers are heated by passing them through the heatersdesignated generally as 100 and 102 of the machine. As can be seen fromFigures 1 and 5, these heaters are of some length so that the plasticrods are heated slowly. The thermoplastic spacers, have rather lowthermal conductivity and it is important that the heating be appliedslowly. As is shown in Figure 9, the heaters, in cross-section comprisean outer U-shaped housing 104 with a strip of heat resistant insulatingmaterial, such as asbestos board 106 on the interior thereof. Theheating elements themselves consist of electrical resistance elements108, which run substantially the length of the housing 104 and which areprovided with suitable wiring 110 for connection to a source ofelectricity not shown. Preferably the elements 108 are of the enclosedtype, commonly known as Calrod elements although they may consist ofopen coils of resistance wire. It is apparent that any form of heatingmay be used so that the heating elements 100 and 102 could be gas-fired,for instance.

After the spacers have passed through the heating elements designated100 and 102, the plastic spacers are heated to the softening point ofthe plastic in each end area and the wire itself has been heated to asufliciently high temperature to insure its being bonded to the plasticmaterial. It is now only necessary to crimp the ends of the spacers toproduce the finished line.

The crimping mechanism has a frame generally indicated as 112 whichconsists of two upright arms designated 114, one of which is located oneach side of the path of travel of the workholders 22. Mounted betweenthe two arms 114 is a rod 116 which is free to rotate and which has atits center a second rod 118 which passes through a hole 120 in rod 116.The hole 120 is sufiiciently large that the rod 118 slips freelytherein. The frame members 114 have located thereon an arm 122 to whichis fastened a spring 124 which biases the rod 118 to the left in Figure5, i. e. opposite to the direction of travel of the workholders 22. Asecond pair of arms 126 is mounted on the frame 122 and these arms 126extend on either side of the path of travel of the workholders as shown.Connecting the two arms 126 is a stop member 128 which extends at aright angle to the path of travel of the workholders, and slightly abovethem. The stop 128 serves to limit the forward motion of the arm 118 andthe mechanism carried by this arm.

Mounted on the rod 118 are a pair of U-shaped members designated 130 and132. U-shaped member 132 is rigidly connected to the arm 118 whilemember 130 is slideably mounted on arm 118. Between the two members 130and 132 is a compression spring 134 which fits over rod 118 and tends tokeep the two members separated.

Mounted on the arms 126 are flat cams 136 which are shaped as shown inFigure 5. The cams 136 each have both an upper cam surface and a lowercam surface. The member 130 has mounted at its lower extremities a pairof rollers 138 each of which contacts a bottom surface of one of thecams 136 while the member 132 has near its upper extremities rollers 140each of which contacts an upper surface of one of cams 136. Mounted nearthe lower extremities of member 130 are two dies 142, and mounted nearthe lower extremities of member 132 are corresponding dies 144. As canbe seen from Figure 8, the die members have a depression 146 cut thereineach of said depressions corresponding to one-fourth of a sphere. Thuswhen a die pair 142 and 144 are brought together the combined dies havea depression therein constituting substantially one-half of a sphere. Itis apparent that when these dies are pressed upon the ends of a heatedspacer passing through the machine, the ends of the spacers will berounded.

Mounted on member 132 is member 148 which is of such a height that itwill clear arm 36 of the workholder 22 but will be engaged by arm 34 ofthe Workholder. Thus, as the workholder comes through the machine, themember 148 will be engaged by the arm 34, causing the members 130 and132, and associated equipment to be drawn along the machine with theworkholder 22. As the members 130 and 132 are drawn along the machine,the spring 134 causes the members 130 and 132 to follow the paths on thecam 136 so that these members are brought closer together and the dieslocated thereon engage the heated ends of the spacer 78. In the centerof the cams, the dies 142 and 144 will be brought completely intoengagement with each other which serves to squeeze the ends of theplastic spacers and to bond them firmly to the wire. After passingthrough the center points of the earns, the arms are again separated bythe action of the cams, releasing the dies from the separators. At aboutthe end of the travel of the cam, the member 148 will become disengagedfrom the arm 34, permitting the crimping mechanism to return againststop 128 and be in a position to repeat the cycle on the next spacerpassing through the machine. It is apparent of course, that the path oftravel of the dies must be slightly shorter than the distance betweenthe adjacent workholders on the endless chain.

The transmission line is now finished, and it is only necessary toremove it from the machine and coil it into rolls of suitable lengths. Aconvenient method of removing the wire from the machine consists of aramp-like member similar to that designated 70 but turned in theopposite direction to the path of travel of the separators. Of course,the ramp should not have a shoulder such as that designated 72.

It will be noted from Figure that the completed transmission line, whichhas been generally designated 150 has spacers which are uniformly placedalong the wires and which have smoothly rounded ends 154. The Wireitself preferably has a coating of a thin, insulating varnish or lacquermaterial designated 156. A suitable coating material is Formvar which isa polyvinyl methylal resin. It has been found that formvar lacqueredwire will not be injured by the heat to which it is exposed in ourdevice and that the Formvar protects the wire from corrosion.

In the use of the process and the machine described herein, anythermoplastic material may be used as the spacer material. However, weprefer to use polystyrene because of its good insulating properties,high mechanical strength and relatively low cost. The wire which may beused is preferably copper wire, although cooperclad steel wire or wiresof other metals may be used.

In one typical operation, the polystyrene rod was inch in diameter andwas cut into sections about 1% inches long and the wires were spaced oneinch between centers by the machine. With'No. 18 wire a transmissionline having a surge impedance of slightly over 400 ohms is producedwhich is suitable for many uses such as television lead-in wire. Ofcourse, other wire spacing may be used, as Well as dilferent wire sizesto produce transmission lines having substantially any desiredimpedance. Normally the spacers are located six inches apart upon thewire although a shorter or longer distance may be used, depending uponthe use to which the wire is to be put.

It will be understood that our invention is not limited to the specificembodiment illustrated and that many variations are possible. Forinstance, instead of the feed and cut-off mechanism shown, the spacersmay be cut to lengths in a separate operation and fed into theworkholders from a hopper.

We claim:

1. In a machine for making open wire transmission line wherein areprovided a-bed, an endless straight line conveyor extendinglongitudinally of said bed, drive means for continuously advancing saidconveyor, a series of Work holders fixedly secured at spaced intervalsalong said conveyor, each of said work holders having a leading armand atrailing arm forming a slot therebetween for receipt of a shortplastic'rod, said slot being normal to the path of travel of saidwork-holders, the leading arms of said work-holders being shorter thanthe trailing arms, means for cutting a slit in either end of each ofsaid plastic rods,. means for inserting a Wire in each of said slits,means positioned thereafter for heating the ends of said plastic rods,and means for crimping the ends of said plastic rods whereby to envelopesaid wires while said ends of said plastic rods are in a heatedcondition, the improvements comprising: means for frictionally engagingan extended length of said plastic rod and means for severing said rodinto individual rods each of a length equivalent to the distance betweensaid end-crimping means; means for reciprocating said rodengaging meansnormal to the bed of said machine, said rod-engaging means frictionallyengaging said rod only when said engaging means advances toward the bedof said machine, said rod-engaging means serving to ad vance an end ofsaid extended length of rod into a position transverse to said conveyorand directly over said conveyor at a height sufiicient that the leadingarm of saidwork holder will pass therebeneath but the trailing arm ofsaid work holder will engage said rod, said severing means beingpositioned about said conveyor and to one side thereof between saidconveyor and said rod engaging means, said severing means comprising acircular saw having drive means therefor and means associated therewithsynchronized with said engaging means whereby said saw is lowered intocontact with a length of rod after said rod is advanced over saidconveyor; support means positioned at either side of said conveyordirectly beneath the area occupied by said length of rod after said feedmeans has advanced said rod, said support means being at least as highas the leading arms of said work holders but lower than the trailingarms of said work holders; resilient means positioned directly abovesaid support means for urging said length of said rod downwardly intocontact with said support means, said support means having ramps leadingdownwardly in the direction of movement of said conveyor, said rampshaving resilient means positioned thereabove for urging rods supportedby said ramps into close engagement therewith whereby a length of rod isfirst severed by said cutting means and thereafter the trailing arm of awork holder mounted on said continuously moving conveyor engages saidlength of rod and advances it down said ramps while said resilient meansmounted above said ramps urges said length of rod into the slot betweenthe arms of said work holder.

2. The structure of claim 1 wherein said crimping means comprises a pairof separable dies on each side of the path of travel of said workholders, said dies being pivoted from a support member positioned oversaid conveyor and means whereby movement of said dies is synchronizedwith movement of said work holders whereby each of said separable diesis moved toward its cooperating die to engage and squeeze the ends ofaplastic rod after said rod has been heated, said dies traveling alongwith said rod as the Work holder advances and thereafter moving apartwhereby to release the ends of said plastic rods, said dies thereafterreturning to a rest position for receipt of the next of said plasticrods carried by said work holders.

(References on following page) 7 8 References Cited in the file of thispatent 2,529,863 Bowen Nov. 14, 1950 Z 577 005 Giacomo Dec. 4 1951PATENT 1 UNITED STATES S 2,579,487 Frankwich Dec. 25, 1951 988,616Anderson Apr. 4, 1911 1,421,168 Charm June 27, 1922 r FOREIGN PATENTS1,440,492 Rankin Jan. 2, 1923 9 920,880 France Apr. 21, 1947 1,783,997Burden Dec. 9, 1930 2,158,496 George May 16, 1939 OTHER REFERENCES2,272,850 Poole Feb, 10, 1942 Modern Plastics, October 1951, page 182.2,471,592 Thomson May 31, 1949

1. IN A MACHINE FOR MAKING OPEN WIRE TRANSMISSION LINE WHEREIN AREPROVIDED A BED, AN ENDLESS STRAIGHT LINE CONVEYOR EXTENDINGLONGITUDINALLY OF SAID BED, DRIVE MEANS FOR CONTINUOUSLY ADVANCING SAIDCONVEYOR, A SERIES OF WORK HOLDERS FIXEDLY SECURED AT SPACED INTERVALSALONG SAID CONVEYOR, EACH OF SAIOD WORK HOLDERS HAVING A LEADING ARM ANDA TRAILING ARM FORMING A SLOT THEREBETWEEN FOR RECEIPT OF A SHORTPLASTIC ROD, SAID SLOT BEING NORMAL TO THE PATH OF TRAVEL OF SAIDWORK-HOLDERS, THE LEADING ARMS OF SAID WORK-HOLDERS BEING SHORTER THANTHE TRAILING ARMS, MEANS FOR CUTTING A SLIT IN EITHER END OF EACH OFSAID PLASTIC RODS, MEANS FOR INSERTING A WIRE IN EACH OF SAID SLITS,MEANS POSITIONED THEREAFTER FOR HEATING THE ENDS OF SAID PLASTIC RODS,AND MEANS FOR CRIMPING THE ENDS OF SAID PLASTIC RODS WHEREBY TO ENVELOPESAID WIRES WHILE SAID ENDS OF SAID PLASTIC RODS ARE IN A HEATEDCONDITION, THE IMPROVEMENTS COMPRISING: MEANS FOR FRICTIONALLY ENGAGINGAN EXTENDED LENGTH OF SAID PLASTIC ROD AND MEANS FOR SEVERING SAID RODINTO INDIVIDUAL RODS EACH OF A LENGTH EQUIVALENT TO THE DISTANCE BETWEENSAID END-CRIMPING MEANS; MEANS FOR RECIPROCATING SAID RODENGAGING MEANSNORMAL TOP THE BED OF SAID MACHINE, SAID ROD-ENGAGING MEANS FRICTIONALLYENGAGING SAID ROD ONLY WHEN SAID ENGAGING MEANS ADVANCES TOWARD THE BEDOF SAID MACHINE, SAID ROD-ENGAGING MEANS SERVING TO ADVANCE AN END OFSAID EXTENDED LENGTH OF ROD INTO A POSITION TRANSVERSE TO SAID CONVEYORAND DIRECTLY OVER SAID CONVEYOR AT A HEIGHT SUFFICEINT THAT THE LEADINGARM OF SAID WORK HOLDER WILL PASS THEREBENEATH BUT THE TRAILING ARM OFSAID WORK HOLDER WILL ENGAGE SAID ROD, SAID SEVERING MEANS BEINGPOSITIONED ABOUT SAID CONVEYOR AND TO ONE SIDE THEREOF BETWEEN SAIDCONVEYOR AND SAID ROD ENGAGING MEANS, SAID SEVERING MEANS COMPRISING ACIRCULAR SAW